Thompson, 19, worked as an auto detailer for Real Clean, a company that provides cleaning services for Patriot Subaru in Saco.

He graduated from Biddeford High School in 2011. Welch, 18, graduated last June from Thornton Academy in Saco and worked at Aroma Joe’s in Biddeford.

She was studying nursing at Southern Maine Community College. They had dated since at least last spring.

Welch, who was called Liv by friends, had been staying with Thompson and his mother, Susan Johnson, at their 17 Sokokis Road apartment for the past month.

“She was a wonderful student and such a sweet person when I had her in class. My heart goes out to her family,” said Misharra Hefler, Welch’s English teacher at Thornton Academy.

Rene Menard, Thorton headmaster, said the academy’s students, staff and alumni are grieving over the tragic and senseless loss

Welch was a cheerleader in her freshman year and on the staff of the student publication, Carpe Diem, in her sophomore year. She took college prep and honors courses in order to study nursing in college.

“All of the deans and guidance counselors who worked with Alivia recall her as a bright student with a sweet disposition who was kind and well-liked by her peers. Our hearts go out to members of her family and all of her friends. A loss like this is felt across the entire community,” Menard said.

L’Heureux, who met Thompson through their shared interest in trucks, said Thompson was passionate about life and fixing up trucks. He was especially fond of modifying trucks so that they sit lower to the ground, like his black GMC with the vanity plate “Slamed,” referring to a car being “slammed” to the ground.

“Anything that was slammed to the ground was his favorite truck,” L’Heureux said. “He loved any truck that was lowered, that was what he was about.”

Thompson didn’t hold grudges, L’Heureux said.

“It didn’t matter who you were, he was always friends with you. Nothing really brought him down,” he said. “(Welch) was pretty much just like him. She was really happy, she didn’t have problems with anyone.”

Ryan Fecteau, who attended high school with Thompson, said Thompson “very rarely would be seen without a smile on his face.”

Friends who posted on Thompson’s Facebook page on Sunday recalled “Walmart adventures,” long car rides and his love of burning tires. “When the snow melts, your burnouts on my road will still be there,” posted one friend, Nate Libby.

Other friends posted comments describing Thompson and Welch as a beautiful couple.

Patriot Subaru released a statement Sunday saying company employees were “shocked and deeply saddened” by the murders.

“Derrick had worked on and off with Patriot, and was close to a number of the associates,” the statement said. “Our sincerest condolences to the families involved, we are grieving for your loss.”